4805 BELVEDERE AVE 2016-01-01 MF Import

Subsurjan Fsploraticn, Geologic Hazard, and Belvedere Lors East Prelimiwry Gtomchnical Enginetring Rrport Everett Washingmn Preliminary Design Rrmmmendationt is conr vous with the footing drain. Roof and surface runoff should not discharge into the (ooting drain system but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to walls should be sloped downward away from the swctures to achieve surface drainage. 15.0 STORM WATER INFILTRATION Storm water infiltration rates under the City oJ Everett Srormwater Ma�wgement Manual is based on the United States Deparunent of Agriculture (USDA) soil texture classification. In order to evaluate the textural classification of soil at this site, one soil sample from each of the exploration pits EP-4 and EP-5 was collected for laboratory sieve analysis. The soil samples analyzed from these locations werc collected below the weathered soil hotizon at depths of appruximately 4 and 6 feet, respectively. Collection of sediments from within the weathered soil horizon was avoided due to the substantially higher silt content of the weathered sediments. The sieve results for these samples indicate that the sediments fall under the USDA classification for sand. Copies of the sieve results are included in the Appendix. According to the Ciry of Everett Stormwater Manageme�nt Manual, the USDA sand classification corresponds to a design i�filtration rate of 8.27 inches per hour. Because infiltration rates established through the USDA textural classification method can be subject to a large degree of error, 5eld infiltration testing was conducted in ace�rdance with the EPA Falling Head Test procedure. Infiltration tests IF-1 and IF-2 were conducted on Lots 33 and 34, adjacent to exploration pits EP-4 and EP-5, approximately where shown on the Site and Exploration Plan, Figure 2. The EPA Falling Head Test procedure utilizes a 6-inch inside-diameter by 4-foot-long section of pipe driven into the soil to a depth of approximately 6 inches. Water is then added to the pipe as necessary to maintain a head of at lr.ast 1 foot over a 4-hour saturation period. After completion of the 4-hour samration period, the pipe is then filled to the top, and the time required for the u�ater in the pipe to fal: every inch down to 6 ioches below the top of the pipe is recorded. The infiltration rate for each of the six, 1-inch intervals is then averaged. The test is then repcated two additional times and the infiltration rate measured for the three tesu are averaged to produce the infiltration rate. The results nf the tests are summarized below in 7'able 5. Afnr�h 5, :004 ASSOCIATElJ EARTN SCIENCES, lNC. rn•w �eu�u»n ��.,��.�nua»>u�ec�wr,x,n P2ge 19